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From: Jan Blunck <jblunck@infradead.org>
Date: Wed, 12 Jul 2017 04:44:28 -0400
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To: Gaetan Rivet <gaetan.rivet@6wind.com>
Cc: dev <dev@dpdk.org>
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Subject: Re: [dpdk-dev] [PATCH v3 4/8] eal: fix hotplug add / remove
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On Tue, Jul 11, 2017 at 7:25 PM, Gaetan Rivet <gaetan.rivet@6wind.com> wrote:
> The hotplug API requires a few properties that were not previously
> explicitly enforced:
>
> - Idempotency, two consecutive scans should result in the same state.
> - Upon returning, internal devices are now allocated and available
> through the new `find_device` operator, meaning that they should be
> identifiable.
>
> The current rte_eal_hotplug_add implementation identifies devices by
> their names, as it is readily available and easy to define.
>
> The device name must be passed to the internal rte_device handle in
> order to be available during scan, when it is then assigned to the
> device. The current way of passing down this information from the device
> declaration is through the global rte_devargs list.
This only true for the virtual bus (vdev).
>
> Furthermore, the rte_device cannot take a bus-specific generated name,
> as it is then not identifiable by the `find_device` operator. The device
> must take the user-defined name. Ideally, an rte_device name should not
> change during its existence.
>
> This commit generates a new rte_devargs associated with the plugged
> device and inserts it in the global rte_devargs list. It consequently
> releases it upon device removal.
So unplugging a device which devargs have been passed via the command
line is implicitly removing the command line parameter? This is a
surprising side-effect and it sound wrong to do. What happens if the
device is getting replugged?
It seems to me that you want to make the hotplug add functionality
behave like a force attach. You can achieve this by calling
rte_eal_devargs_add/parse before calling into hotplug add.
> Fixes: a3ee360f4440 ("eal: add hotplug add/remove device")
>
> Signed-off-by: Gaetan Rivet <gaetan.rivet@6wind.com>
> ---
> lib/librte_eal/common/eal_common_dev.c | 57 ++++++++++++++++++++++++++++++++--
> 1 file changed, 54 insertions(+), 3 deletions(-)
>
> diff --git a/lib/librte_eal/common/eal_common_dev.c b/lib/librte_eal/common/eal_common_dev.c
> index 32e12b5..f5566a6 100644
> --- a/lib/librte_eal/common/eal_common_dev.c
> +++ b/lib/librte_eal/common/eal_common_dev.c
> @@ -118,11 +118,32 @@ int rte_eal_dev_detach(struct rte_device *dev)
> return ret;
> }
>
> +static char *
> +full_dev_name(const char *bus, const char *dev, const char *args)
> +{
> + char *name;
> + size_t len;
> +
> + len = strlen(bus) + 1 +
> + strlen(dev) + 1 +
> + strlen(args) + 1;
> + name = calloc(1, len);
> + if (name == NULL) {
> + RTE_LOG(ERR, EAL, "Could not allocate full device name\n");
> + return NULL;
> + }
> + snprintf(name, len, "%s:%s,%s", bus, dev,
> + args ? args : "");
> + return name;
> +}
> +
> int rte_eal_hotplug_add(const char *busname, const char *devname,
> const char *devargs)
> {
> struct rte_bus *bus;
> struct rte_device *dev;
> + struct rte_devargs *da;
> + char *name;
> int ret;
>
> bus = rte_bus_find_by_name(busname);
> @@ -137,21 +158,49 @@ int rte_eal_hotplug_add(const char *busname, const char *devname,
> return -ENOTSUP;
> }
>
> + name = full_dev_name(busname, devname, devargs);
> + if (name == NULL)
> + return -ENOMEM;
> +
> + da = calloc(1, sizeof(*da));
> + if (da == NULL) {
> + ret = -ENOMEM;
> + goto err_name;
> + }
> +
> + ret = rte_eal_devargs_parse(name, da);
> + if (ret)
> + goto err_devarg;
> +
> + ret = rte_eal_devargs_insert(da);
> + if (ret)
> + goto err_devarg;
> +
> ret = bus->scan();
> if (ret)
> - return ret;
> + goto err_devarg;
>
> dev = bus->find_device(NULL, cmp_detached_dev_name, devname);
> if (dev == NULL) {
> RTE_LOG(ERR, EAL, "Cannot find unplugged device (%s)\n",
> devname);
> - return -EINVAL;
> + ret = -ENODEV;
> + goto err_devarg;
> }
>
> ret = bus->plug(dev, devargs);
> - if (ret)
> + if (ret) {
> RTE_LOG(ERR, EAL, "Driver cannot attach the device (%s)\n",
> dev->name);
> + goto err_devarg;
> + }
> + free(name);
> + return 0;
> +
> +err_devarg:
> + rte_eal_devargs_remove(busname, devname);
> +err_name:
> + free(name);
> return ret;
> }
>
> @@ -179,6 +228,8 @@ int rte_eal_hotplug_remove(const char *busname, const char *devname)
> return -EINVAL;
> }
>
> + rte_eal_devargs_remove(busname, devname);
> + dev->devargs = NULL;
> ret = bus->unplug(dev);
> if (ret)
> RTE_LOG(ERR, EAL, "Driver cannot detach the device (%s)\n",
> --
> 2.1.4
>